The desirability of using ceramic materials in heat exchangers has been recognized, however, attempts to provide practical, effective, long life, low cost and reliable heat exchangers of annular configuration employing ceramic materials have not heretofore been entirely successful. Among the difficulties encountered are those relating to maintaining a long-lived and effective seal between the ceramic materials and the metallic mounting means therefor. This is due, in part at least, to the different coefficients of thermal expansion of the different materials. To operate efficiently, the two fluid streams of a heat exchanger must be isolated from each other and not allowed to leak. Leakage has typically been a problem at the interface of the near zero thermal growth ceramic material and the metallic mounting means.
Moreover, another sealing difficulty arises when attempting to provide heat exchangers of annular configuration using ceramic materials. A low cost, continuously annular ceramic construction is not possible with current processing techniques. A low cost and desirable ceramic heat exchanger element that can be readily used is a pre-assembled block made from a plurality of suitably configured ceramic plates stacked together. When such blocks are arranged in a near-annular array as required for a heat exchanger of annular configuration such blocks do not form a continuous circle of ceramic material. The gaps between the blocks introduce additional sealing problems.